1. Field of the Invention
The present invention relates to a rotary electric shaver wherein an inner cutter rotates while, from below, sliding against a plurality of outer cutters provided coaxially.
2. Description of the Related Art
For some time, rotary electric shavers of the so-called two-track (double track) type, having two tracks (ring-shaped channels wherein the inner cutter travels) provided coaxially in a ring-shaped outer cutter, have been widely used. Here, the two tracks are provided in one common outer cutter, and the two inner circumferential and outer circumferential tracks are corresponding. The inner cutter that slides against these two tracks is also formed integrally. That is, the inner cutter is such that an outside inner cutter that slides against the outer circumferential track and an inside inner cutter that slides against the inner circumferential track are made integral therein, this inner cutter is made to engage from above with a drive shaft that is urged upward, and the inner cutter presses against the outer cutter due to the upward return force on the drive shaft.
With this conventional shaver, there is a problem that because the outer cutter is made integral, the entire surface contacting the skin will move up and down in correspondence with irregularities in the skin surface, but the outer cutter cannot minutely follow the fine irregularities in the skin surface.
Thereupon, in Japanese Patent Application Laid-Open Nos. 2001-755 and 55-158084, for example, it is proposed that the outer cutter be divided so as to correspond to inner and outer circumferential tracks, making an inside outer cutter and an outside outer cutter capable of independently moving up and down.
In the shavers disclosed in Japanese Patent Application Laid-Open Nos. 2001-755 and 55-158084, the outer cutter is divided between the inner and the outer circumference, but the inner cutter support structure is very complex, the number of parts is extremely large, and the shavers become large and bulky. In the shavers described in Japanese Patent Application Laid-Open Nos. 2001-755 and 55-158084, holder units for the outside inner cutter and the inside inner cutter are formed in tubular shapes on the same axis, and these tubular holder units are driven by a motor. Furthermore, springs for urging the respective tubular holder units upward are accommodated inside these tubular holder units. As a consequence, the size becomes larger, with the up-and-down dimension and the diameter of the support portion of the inner cutter becoming large. Furthermore, because the structure is complex, there are other problems, such as the assembly is difficult and the number of assembly operations is increased, it is very difficult to effect a water-resistant structure, and cleaning out whisker shavings is also difficult.
Moreover, because the structure of the drive system for transmitting the rotation of the motor to the inner cutter differs drastically from the conventional structure wherein an upward return force is imparted to the drive shaft, a dedicated design becomes necessary, and it becomes necessary also to introduce new manufacturing equipment.